Web tracking system

ABSTRACT

A web tracking system for a continuous web of material which is transported from a supply to a takeup means along a predetermined path via one or more processing stations and comprises aligned tracking indicia along at least one edge of the web. Means are provided to observe the tracking indica as the web is transported along the system path and produce information either indicative of dimensional changes in the length and width of the web due to web shrinkage or expansion or indicative of a particular point along the length of the web useful at one or more of the processing stations in the system.

RELATED APPLICATION

U.S. Application Ser. No. 444,144, filed Nov. 24, 1982 and entitledCOLOR ELECTROGRAPHIC RECORDING APPARATUS and assigned to the assigneeherein.

BACKGROUND OF THE INVENTION

The present invention relates to the transport of a continuous web ofmaterial and more particularly to a system and method for tracking ofthe web in its path of movement from a supply to a takeup means.

Many different kinds of systems have been devised to track the movementof a web of material in order to positively determine, for example,various locations along its length so that one or more operations may beperformed in connection with the treatment of the web. In carrying outthe treatment, the path of the web may have to be monitored to ensurethat it .[.mantains.]. .Iadd.maintains .Iaddend.a predetermined path inthe system for processing at one or more system stations. This mayentail optical monitoring means and lateral translation of the web inthe system path or lateral translation of the web supply roll to providefor misalignment correction.

Also, the web may change in physical size, i.e., it will stretch orexpand, or shrink or contract both laterally and longitudinally relativeto its length. Such expansion or shrinkage is due to several factors.The major factors are environmental conditions, e.g., temperature andhumidity, web handling in the system and the resultant action of theparticular processes being performed in connection with the web, e.g.,the application of a fluid to the surface of the web.

In the usual case of web material, e.g., electrographic recording mediumcomprising dielectric coated paper, the web can stretch or shrink asmuch as 1 mil per foot and the dimensional change laterally across thistype of material can be three times greater than the dimensional changealong the longitudinal extent of the material. Web material isacceptable to such dimensional changes due to the manner by which it ismade. For example, in the case of paper, the fiberous grain of the paperis such that it can stretch or shrink more in one orthogonal directionas compared to another. Web material such as polyester based films maynot stretch or shrink as much as paper, but are still succeptable tosome stretching and shrinkage.

Further, web material may neither be perfectly flat or straight nor arethe web material edges exactly parallel to one another.

These web dimensional changes and physical irregularities which mayoccur while the web material is moving through a web processing systemcan contribute significantly to the successful application of thedesired process.

While one solution to this problem might be to require tighterspecifications in the design and manufacture of web material withoutthese irregularities, this would not be desirable because of the highcosts to provide such quality control in its manufacture, which wouldnot be acceptable to web material manufacturers. The better approach isto create a tracking system that can cope with these irregularities andcapable of monitoring and controlling the station functions withoutrequiring changes to the web material.

SUMMARY OF THE INVENTION

According to this invention, a system and method is provided formonitoring tracking indica provided on the web material, preferrablyalong one or more of its edges, and developing signals representative ofweb dimensional changes for application at one or more web processingstations taking into account the changes in web physical parameters.

The web tracking system of this invention is for a continuous web ofmaterial which is transported from a supply to a takeup means along apredetermined path via one or more processing stations comprisingaligned tracking .[.indica.]. .Iadd.indicia .Iaddend.along at least oneedge of the web. Means is provided to observe the tracking .[.indica.]..Iadd.indicia .Iaddend.as the web is transported along the system pathand produce information indicative of dimensional changes in the lengthof the web or indicative of a particular point along the length of theweb, which information is useful at one or more of the processingstations. The aforementioned means includes optical sensing of thetracking .[.indica.]. .Iadd.indicia .Iaddend.provide electrical signalsrepresentative of the tracking indicia.

Means associated with the transport of the web photoelectrically sensesthe aligned tracking indicia and provides electrical signalsrepresentative of information as to the dimensional extent bothlaterally and longitudinally of the web being handled by the system anduseful, for example, to provide adjustment for both lateral andlongitudinal dimension of the web through the operation of a steppermotor via a position control that processes and interprets theelectrical signals representative of the indicia.

One aspect of the associated means is to provide relative translationbetween the web and a processing station on-the-fly as the web is beingprocessed at the station. This may be possibly exemplified in severalways. First, the supply roll from which the web is paid out into thesystem may be laterally translated relative to the web path through thesystem and the system work stations. Secondly, a processing station maybe laterally translated relative to the web. Third, the processingstation or component at the station may be rotated relative to the pathof the web through the system.

Another aspect of the associated mean is to control the rate of movementof the web along its path based upon the sensed information relative tothe tracking indicia.

The tracking indicia may comprise an aligned series of registrationmarks having the same dimensional spacing and width adjacent one edge oradjacent both edges of the web. The registration marks may be preceededby a plurality of aligned initializing marks for which have a differentgeometric shape compared to the registration marks, e.g., a differentmark width. The point of change from the last narrower initializing markto the first wider registration mark can be indicative of the startingpoint on the web for a particular treatment to be applied at a selectedprocessing station.

Lateral and longitudinal dimensional changes in the web drived fromobservation of an aligned row of registration marks is indicative ofchanges in length, either expansion or shrinkage, of the web underobservation. In this regard, it should be noted that coarse correctionfor lateral alignment of the web relative to a processing station due toweb shifting in the system path can be accomplished by the lateraltranslation of the web supply roll while fine correction for lateral.Iadd.alignment .Iaddend.due to web expansion or shrinkage can beaccomplished by the lateral translation of a processing station or acomponent at the station to recenter the station relative to the web.

Alternatively, a tracking line adjacent to and parallel with the alignedrow of registration marks at both edges of the web may be employed forlateral station translation.

Other objects and attainments together with a fuller understanding ofthe invention will become apparent and appreciated by referring to thefollowing description and claims taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a web tracking system according tothis invention.

FIG. 2 is a schematic diagram showing a plan view of a portion of thesystem shown in FIG. 1.

FIG. 3 is a schematic diagram of the means for lateral translation ofthe web supply roll in the system of FIG. 1.

FIG. 4 is a section taken along the line of 4--4 of FIG. 3 showing aside view of the web edge detector used with the lateral translationmeans of FIG. 3.

FIG. 5 is a plan view of portion of a web section illustrating trackingindicia of this invention.

FIG. 6 is a plan of one embodiment of tracking indicia as applied to theweb and as arranged with X and Y photosensors.

FIG. 7 is a plan view of another embodiment of tracking indicia asapplied to the web.

FIG. 8 is a plan view of the same embodiment of tracking indicia asdisclosed in FIG. 7 but with a different X and Y photosensorarrangement.

FIGS. 9A and 9B are circuit diagrams for the development of electricalsignals representative of the output from the Y photosensors.

FIG. 10 is a circuit logic diagram for the development of electricalsignals representative of the X photosensors.

FIG. 11 is a circuit diagram for use in the determination of thebeginning point for web processing at a processing station.

FIG. 12 is a circuit diagram for the web guide servo control in FIG. 1to provide latent translation of the web supply roll.

FIGS. 13A and 13B are circuit diagrams for any one of the positioncontrols shown in FIG. 1 to provide stepped correction signals basedupon tracking indicia information to a servo drive motor.

FIG. 14 is a circuit diagram for any one of the position controls shownin FIG. 1 to provide stepped correction signals based upon trackingindicia information that have been adjusted for signal noise.

FIG. 15 is another circuit diagram for any one of the position controlsshown in FIG. 1 to provide stepped correction signals based upontracking indicia information that have been adjusted for signal noise.

FIG. 16 is a detailed schematic diagram of an embodiment for the tensionservo control shown in FIG. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Referring to FIGS. 1 and 2 there is diagrammatically shown system 10 ofthis invention. System 10 comprises .[.a.]. one or more processingstations 12, 14 16. Stations 12-16 are aligned in the path of web 18.Web 18 is drawn from supply roll 20 in the X direction over a series ofrolls in the bed of system 10, by means of drive roll 22 driven by drivemotor 24. These rolls are shown at 26 and 28. A series of rollers 30 areprovided to ride against drive roll 22 in order to provide a firm gripon the web 18. The web 18 is taken up on take-up roll 32 driven bytake-up motor 34.

Supply roll 20 is also provided with a drive motor 19 to rewind the paidout web 18 back onto supply roll 20 for further processing by systemstations 12-16. The drive motor circuitry for rolls 20 and 32 is notshown, as such web handling is conventional in the continuous webhandling art involving the manufacturing, coating, utilizing (e.g., reelto reel recording tape transport) and other processing of continuous webmaterial. Basically, supply roll motor 19 is continuously applying adriving force in the direction of arrow 20' while take up motor 34 iscontinuously applying drive in the direction of arrow 32'. Theseoppositely opposed drives maintain web 18 in a state of equilibriumuntil drive motor 24 is enabled in either direction, as indicated byarrow 24', either to drive the web 18 forward at a relatively slow ratefor processing by system 10 or to drive the web 18 reward at arelatively fast rate to wind the web 18 back onto supply roll 20. Driveservo control 48 drives and controls the speed and direction of drivemotor 24 via line 50. Control 48 maintains selected motor speed byutilizing a speed servo loop including tachometer 52, the output ofwhich is connected to control 48 via line 54. This type of control isconventional in the web handling art.

Encoder 36, backed by roller 38, is adapted to run with the moving web18 and may be positioned at any convenient location along the web paththrough system 10. The output of encoder 36 is supplied to each of theposition control circuits 42 and 44 and to a control circuit 46 via line40. Encoder 36 provides a series of pulses per revolution, each pulserepresentative of an incremental distance of web movement.

The position control circuits 42 and 44 provide direction and correctionpulses on respective line 56 and 58 to respective servo stepper motors62 and 64 and control circuit 46 provides correction pulses on line 60to processing station 16 to provide a desired correcting function. Servostepper motors 62 and 64 in turn provide a desired servo function atrespective stations 12 and 14.

As shown in FIGS. 1 and 2, pairs of photosensors X, Y, X', and Y' arepositioned adjacent to the web 18 and preceeding the stations 12-14.These photosensors are actually pairs of photodiodes coupled at theircathode to a source of positive bias. Photosensor X comprisesphotodiodes 1X and 2X, photosensor X' comprises photodiodes 1X' and 2X',photosensor Y comprises photodiodes 1Y and 2Y and photosensor Y'comprises photodiodes 1Y' and 2Y'. These photosensors need not bepositioned between the encoder 36 and the first statation 12. They mayalso be positioned in other locations along the path length of system 10such as, for example, between stations 14 and 16. However, it ispreferred that they be positioned in relatively close proximity tostations 12-16 since their detection capabilities relative to web 18will be put to utilization at one or more of the stations.

Phototsensors X, X', Y and Y' also each include their own light sourcedirected toward the web surface 17, which light sources are not depictedin the Figures.

As shown in FIG, 2 the photosensors X, Y, X' and Y' are physicallymounted beneath the surface 17 of web 18 in a manner to be substantiallyaligned with the tracking indicia 70 which comprises a series of edgetracking marks 72 and 74 and two tracking lines 76 and 78. Sensor X isin a position to sense tracking marks 72. Sensor Y is in a position tosense tracking line 76, sensor X' is in a position to sense trackingmarks 74 and sensor Y' is in a position to sense tacking line 78. As thesurface 17 of web is drawn through the processing stations, the sensorsX, X', Y and Y' and connected signal processing circuitry can monitorthe indicia and utilize the information for various station functions.

As shown in FIG. 1, sensors Y and Y' have their respective outputs 80and 82 connected to control circuits 42, 44 and 46. Sensors X and X'have their respective outputs 84 and 86 also connected to controlcircuits 42, 44 and 46.

Adjacent to the payout of web 18 from supply roll 20 is dancer roll 90,which is supported in a conventional manner to provide predeterminedlevel of bias on web 18 indicated by arrow 92. Means 94 is provided tomonitor the applied predetermined tension .Iadd.by .Iaddend.dancer roll90. Means 94 may be an optical sensor positioned to determine relativevertical movement of dancer roll 90. On the other hand, means 94 may bean electrical sensor to determine such movement. Such an embodiment isillustrated in FIG. 16, which will be discussed later. Means 94 isconnected by line 96 to tension servo control 98. Control 98, whichincludes a motor drive control, is coupled via line 100 to supply rollmotor 19.

The function of dancer roll 90 is to ensure that a predetermined amountof tension is applied to web 18 as it is paid off of supply roll 20. Theservo control 98 can monitor changes in the desired tension and eitherincrease or decrease the back torque on motor 19, as the case may be,for correcting to the desired level of web tension.

Y adjustment for web 18, i.e., lateral adjustment of web positionrelative to processing stations 12-16, is achieved by a supply rollposition actuator 102 shown in further detail in FIGS. 3 and 12. Theactuator 102 includes step servo motor which receives input from the webguide servo control 106 via supply lines 104 to move the supply roll 20laterally in either Y direction. An optical edge sensor 110 monitors theedge of web 18 and supplies an input via line 108 to web guide servocontrol 106 indicative of which direction the supply roll should belaterally moved for desired Y web alignment.

Reference is now made to FIGS. 3 and 4 to explain in further detail theY direction supply roll alignment. Supply roll 20 is rotatably supportedin side frames 140 and 142 on a structure comprising roll tube 180having end roll stops 181 and 182. Stops 181 and 182 support roll 18 ontube 180 with the aid of a roll spacer 183. Roll stop 181 is secured totube 180 while stop 182 is removable. An externally threaded collar 184is secured to the end of tube 180 opposite to stop 181. Once roll 18 isslipped over tube 180 and guide 183 with its end in engagement with stop181, the removable stop 182 is slipped over collar 184 and held inposition by means of roll nut 185 threaded upon collar 184. In thismanner, supply roll 18 is held secured onto tube 180.

Left and right ends of roll tube 180 are provided with a respectivebearing support members 186 and 187. Member 186 has a cylindricalpassage 189 within which is slidably mounted the roll thrust plunger188. The rearward extent of plunger 188 is provided with a circularprojection 190.

Mounted internally within tube 180 is a plunger spring stop 191. Stop191 is provided with a circular detent 192. Compression spring 193 ismounted between plunger projection 190 and stop detent 192 to urgeplunger 188 out of passage 189. However, plunger 188 is held withinpassage 189 by means of stop ring 186A.

The forward end of plunger 188 is provided with a pointed projection 194that contacts the end extension 195A of motor drive shaft 195. Shaft 195is driven by supply roll motor 19.

Secured to the end of drive shaft 195 is a drive torque coupler 196.Formed on the outer end of bearing support member 186 is a roll coupler197. Couplers 196 and 197 each have respectively one or more extensions196' or 197' that will come into engagement with a correspondingcomplement extension on the other when rotational movement is applied ineither direction to shaft 195. Thus, upon rotation of drive shaft 195, acoupler extension 196' of coupler 196 will come into contact with acorresponding extension 197' on roll coupler 197 so that roll tube 180will be rotatably driven by shaft 195. Biased plunger 188 functions tomaintain the couplers 196 and 197 in firm engagement with one anotherwithout interfering with the rotary operation of roll tube 180.

Bearing support member 186 is supported in roll sleeve bearing 198,which is supported in mount 190 which is part of side frame 142. Bearingsupport member 187 is supported at the other end of roll tube 180 inroll sleeve bearing 198A, which is supported in mount 202 which is partof side frame 140.

The end of bearing support member 187 is provided with a plug member 203having a spherical end surface 204.

It should be noted that the bearing support members 186 and 187 may besupported in U-shaped or open ended bearings 198 and 198A. In thismanner, the entire supply roll tube 180 may be easily inserted with itscoupler end positioned (intercoupling of couplers 196 and 197) intoplace on bearing 198 followed by insertion of the other end of roll tube180 at support 187 on bearing 198A. Spherical end surface 204 will ridesmoothly over the forward end of threaded screw 208 due to the biasaction of plunger 188. This action eliminates any damages that might becaused to the actuactor 102 upon insertion of the roll tube 180 ontobearings 198 and 198A.

Position actuator 102 comprises stepper motor 205 which is mounted on aframe plate 206 via bolts 213. The output shaft 207 of motor 205 securedto threaded roll drive screw 208. Screw 208 is provided with an externalthread of predetermined pitch. An opening 210 is provided in side frame140 into which is mounted an internally threaded bushing 211 and issecured to frame 140 by means of fasteners 212. Threaded bushing 211 hasthe same thread pitch as drive screw 208 so that upon rotationalmovement of motor shaft 207, the drive screw 208 will move laterallyaway from or against plug member 203 depending on the direction ofrotation of shaft 207. In order to provide for this translatory motion,stepper motor 205 must be mounter to move with the translatory motion ofdrive screw 208. This is accomplished through movably mounted frameplate 206.

Frame plate 206 comprises a flat plate with a pin 214 extending fromeach plate corner. The pin members 214 are slidably positionable incorresponding openings 215 formed in side frame 140. Operation of motor205 will cause translatory motion of drive screw 208 along the axis 199of roll tube 180 so that the supply roll 20 can be positioned in the Ydirection for lateral alignment of the web 18 as it is fed into theprocessing station 12. This translatory motion can be applied to rolltube 180 independent of the rotational opertion of the roll tube 180 bysupply roll motor 19 via shaft 195 and the extended couplers 196 and197.

Limit switch device 216 is mounted on side frame 140. Like devices 150and 152, device 216 is provided with two optical sensor and light sourcepairs respectively at 217 and 218. A flag 220 is mounted on the top edgeof frame plate 206. Upon continuous operation of stepper motor 205 ineither direction, flag 220 will eventually insert the light source beamto a respective sensor causing termination of the operation of motor 205via web guide servo control circuit 106. Thus, sensor/light source pairs217 and 218 represent the maximum limits of translatory motion foractuator 102.

The respective outputs 221 and 222 of sensor/source pairs 217 and 218are supplied as inputs to circuit 168. As previously indicated, opticaledge sensor 110 has its output on line 167 connected to circuit 168.

As shown in FIG. 4, sensor 110 comprises a U-shaped frame 223 with alight source 224 mounted on one leg of the frame in oppositely opposedrelation to a photosensor 225 mounted on the other leg of frame 223.Sensor 110 is mounted relative to side frame 140. The sensor 110 isemployed in a manner so that it is midway between a position whereinphotosensor 225 detects full illumination from source 224, i.e., the web18 is not in the path of the light source 224 and a position whereinphotosensor 225 is completely blocked off from the illumination fromsource 224, i.e., the web 18 is completely in the path of the lightsource 224.

Circuit 106 performs to basic functions: an optical sensor interface andstepper control. These functions will be further detailed in connectionwith the description of FIG. 12. In general, the operation of steppermotor 205 is such that upon activation via circuit 106, motor 205 isdriven to translate roll tube 180 to the inner maximum limit until flag220 intersects the light beam of sensor/source pair 217 which stops theoperation of motor 205. Motor 205 is then operated a predeterminedamount in the opposite direction to the proximate midpoint wherein theedge of web 18 is halfway over photosensor 225. At this point, flag 220is about half way between pairs 217 and 218. The sensor interface ofcircuit 102 includes a comparator having one input from photosensor 225and another input from a voltage reference, V_(REF). V_(REF) representsin electrical quantity, the coarse Y position desired for web 18. Thevoltage value from photosensor 225 via line 169 is compared with V_(REF)to determine if stepper control should be activated to roll readjust theposition of tube 180 along the Y direction and reposition the web edgeas the web is being paid off of supply roll 20. As an example, themagnitude of adjustment of supply roll translation may be plus or minus10 mils. Stepper motor provides 240 steps revolution of its outputshaft. If the thread pitch of drive screw 208 is 10 turns per inch, thenone revolution of the output of motor 205 comprises about 2000 steps perinch and each step of motor 205 is 0.5 mil translatory step.

Explanation will now be directed to the registration means for providingstepper motor control signals or correction signals to desiredadjustments at processing stations 12-16. The adjustments to beaccomplished are based upon optical monitoring of tracking indicia 70 onthe web surface 17. In order to properly understand this registrationmeans, a sufficient comprehension of the tracking indicia should berealized.

In FIG. 5, an edge section of recording web 18 is shown. Within thefield 15 of the web 18 is shown an area 69 to be treated by one or moreprocesses at the respective processing stations 12-16. Such processescould include specialized coating or web surface treatment or printing.

As previously indicated in connection with the description of FIG. 2,tracking indicia 70 includes registration marks 72 and tracking line 76.The registration marks 72 are of equal width and separated by a spaceequal to their width. The marks 72 are employed to determine dimensionalchanges of web 18 in the X direction. The tracking line 76, togetherwith tracking line 78 on the opposite edge of the web 18, are employedto determine dimensional changes of web 18 in the Y direction.

Mention should be made of the fact that tracking indicia 70 may bepreprinted on the web surface 17 or printed at the time of webprocessing. In the latter case, one of the stations 12-16 may be aprinting station for the indicia which are printed prior to webtreatment at the other stations.

Also, it should be realized that as an alternative to printed indicia70, a series of rectangular perforations adjacent one or both edges ofweb 18 may be utilized as tracking indicia. In this embodiment, thelight source for the photosensors X, X', Y, and Y' would be positionedon the top side of the web in oppositely opposed relation to one or morephotosensors.

Means may be provided to determine the precise point wherein webtreatment will commence on web 18. This point is indicated by arrow 79in FIG. 5 and is the start point. This point is calculated by thedetermination point of the first registration mark 77 after theidentification of a series of initializing marks 71 before the beginningof the line of registration marks 72. The initializing marks 71 are usedto perform two functions. The first function is to permit the starttreatment circuitry of FIG. 11 to determine if the circuitry is, infact, identifying purposeful marks formed on the web, vis a vis othermarks, such as scratch marks or foreign marks present on the web surface17. Once the circuitry has recognized that it has detected the series ofinitializing marks 71, then the circuitry can be enabled to determinethe START TREATMENT point at 79. This determination is made from thetransition from the last narrow initializing mark 75 to the first widerregistration mark 77. This change of interval spacing is represented bypointer 79. Once this change has been recognized by the circuitry, thepoint 79 of START TREATMENT can be precisely determined. The circuitryis designed to count pulses produced by encoder 36. Pulses are countedbetween transitions from the point where a pair of photosensors detect abalanced condition of light to the next balanced condition of light. Forexample, the initializing marks 71 may be one third the size or width ofthe registration marks 72. This means that for a cycle from one lightbalanced condition to the next, there will N encoder pulses counted bythe circuitry. This is less counted pulses than is detected for thecycle generated from the registration marks which will be about twothirds longer or equal to N+2/3N. This difference in the number ofcounted encoder pulses in transition from mark 75 to mark 77 is employedto determine where the START TREATMENT point 79 will begin on web 18.

Before discussing circuitry relating to initializing mark determinationand START TREATMENT determination, reference will be made to therelationship of the photosensors X, Y, X' and Y' to the tracking indicia70 (FIGS. 6, 7 and 8) and the initial photosensor signal processingcircuitry for the electrical signals received from these photosensors(FIGS. 9 and 10).

The tracking indicia 70 shown in FIG. 2 is shown in enlarged detail inFIG. 6. For determining web dimensional changes in the X direction, aseries of registration marks 72 are needed only along one edge of theweb. With these registration marks 72 and 74 provided along both edgesof the web, however, it is believed that improved discernment of suchchanges may be possible. Also, skewing of the web along its path throughsystem 10 can be discerned and station θ (rotational) position changescan be considered.

For determining web dimensional changes in the Y direction, a pair oftracking lines 76 and 78 are provided, one along each web edge. Bymonitoring positional changes in the Y direction of line 76 relative tophotosensor Y and line 78 relative to photosensor Y', it is possible todetermine if the web 18 has expanded or contracted.

To discern web dimensional changes in the X direction, the controlcircuitry 42 or 44 will be constantly counting up encoder pulses fromencoder 36 between light balance conditions of an X and/or X'photosensor pair. For example, in FIG. 6, the photosensor pair 1X' and2X' are shown at this balanced transition point. As the web moves to thenext such transition point, completing a cycle 240, the number of pulsesreceived and from the encoder 36 will be indicative of (1) nodimensional changes (an expected count has been received), (2) ashrinkage of the web has occurred (an insufficient number below theexpected count has been received), or (3) a stretch or expansion of theweb has occurred (a larger amount number than expected count has beenreceived) In the actual embodiment employed, the expected count is 448encoder pulses within the time of a cycle represented by the distance240.

To discern web dimensional changes in the Y direction, the controlcircuitry 42 or 44 will be monitoring light balance conditions ofphotsensors Y and Y' so that if these sensor pairs are straddled equallyover their respective tracking lines 76 and 78, a balance condition willexist. If the sensor pairs indicate a change wherein either or bothsensors 2Y and/or 1Y' sense more light than their companion sensors 1Yand 2Y', then there has been a detected expansion of the web in the Ydirection. Y translation of processing stations 12 or 14 or a componentpart of those stations may be initiated for relative Y movement until abalanced condition is reached relative to the total light received fromboth the Y and Y' photosensors.

If the sensor pairs indicate a change wherein either or both sensors 1Yand/or 2Y' sense more light than their companion snesors 2Y and 1Y',then there has been a detected shrinkage of the web in the Y direction.Y translation of the processing station or station component may beinitiated until a balanced condition is reached relative to the totallight received from both the Y and Y' photosensors.

To discern a skew in the position of web 18, the control circuitry 42 or44 will be monitoring the light balance conditions along both lines ofregistration marks 72 and 74. If the count of encoder pulses per cycle240 differ along one side relative to the other so that there is, forexample, a higher expected count on one side as compared to an expectedcount or a lower than expected count on the other side, then there hasbeen a detected skew of the web in its path through the system 10. The θtranslation of a processing station 12 or 14 or station component may beinitiated until a balanced condition is reached relative to the totallight received from both the Y and Y' photosensors.

In the alternative embodiment of FIGS. 7 and 8, the tracking lines 76and 78 can be eliminated and the tracking mark lines consisting of theseries of marks 72A and 74A may provide both X, Y and θ monitoringfunctions as in the case of the embodiment shown in FIG. 6. The Y and Y'photosensors employ the lines of marks 72A and 74A as a means todetermine expansion and shrinkage conditions of the web in the Ydirection while the X and X' photosensors employ the spaced marks 72Aand 74A to determine the number of encoder pulses occurring per cycle240 for determination of expansion and shrinkage conditions in the Xdirection as well as web skew conditions.

The same lines of marks 72A and 74A are shown in the embodiment of FIG.8. However, in FIG. 8, photosensors 121 and 121' are quad sensors. Thecombination of quad sensors 121A and C and 121 B and D; 121' A and C and121'B and D perform the functions of sensors 1Y and 2Y; 1Y' and 2Y',respectively. The combination quad sensors 121 A and B and 121 C and D;121' A and B and 121' C and D perform the functions of sensors 1X and2X; 1X' and 2X', respectively. FIG. 9 shows the initial signalprocessing circuitry for the Y and Y' photosensors. This circuit may beat the Y and Y' photosensors or part of the circuit at the postioncontrol 42 or 44. The cathodes of photosensors 1Y and 2Y; 1Y' and 2Y'are connected together to a positive voltage source. The anodes of thesesensor pairs are connected to the inverting input of a conventionaloperational amplifiers 242. The feedback RC filters 242' on theseamplifiers provide low bandwidth on the input signals from thephotosensors Y and Y'. The output of the amplifiers 242 is supplied viaisolation resistors 243 and respective lines 248, 249, 250 and 251, viasumming resistors 244 to a summary node 245 which is connected to aninput of summing amplifiers 246. The other input of amplifiers 246 isconnected to a reference voltage, e.g., --5.6 volts. The output of thesumming amplifers 246 is connected via isolation resistors and apositive voltage bias to the noninverting inputs of operationalamplifiers 242. The purpose of this feedback is to provide for automaticstabilizing of the sensed inputs independent of different light levelsthat the photosensors Y and Y' might receive from the provided lightsources. The magnitude of light from the sources will vary or decreaseover a period of time. The feedback amplifiers 246 endeavor to maintainthe summing nodes 245 at the same voltage as the reference voltage,e.g., --5.6 volts so that the output voltages of amplifiers 242 arealways at the same desired levels regardless of changes in light sourceintensities over a period of time.

The adjusted outputs on lines 249 and 251 for photosensors 2Y and 2Y'respectively are supplied to summary node 252 via summing resistors 253.The adjusted outputs on lines 248 and 250 for photosensors 1Y and 1Y'respectively are supplied to summing node 254 via summing resistors 255.The summed voltage value at node 252 is supplied to the noninvertinginput of linear differential amplifier 256 while the summed voltagevalue at node 254 is supplied to the inverting input of amplifier 256.The output on line 257 of amplifier 256 is thus representative of anydifferences in light level conditions determined by sensors 2Y and 2Y'as compared to sensors 1Y and 1Y'. This difference may be representativeof left or right corrections relative to web position, as the voltage onoutput line 257 goes above or below the reference of --5.6 volts placedon the noninverting input at node 252. High gain differential comarator260 receives the output 257 as an input and this comparator is alsoreferenced to the reference voltage of --5.6 volts, being its otherinput. Comparator 260, therefore, makes a sharp determination that theoutput on line 257 is above or below the reference voltage.

The output on line 257 of linear differential amplifier 256 is filteredby RC filter 258 and is, as previously indicated, an input to the highgain differential comparator 260. The other input of comparator 260 isconnected to the reference voltage --5.6 volts. Comparator 260 has asmall band of sensitivity so that very small changes on line 257 eitherpositive or negative relative to the reference input to comparator 260will provide a corresponding negative or positive output voltage on line261. Feedback resistor 260A for comparator provides a hysteresisoperating effect for differential comparator 260. The output ofdifferential comparator 260 on line 261 is supplied as an input to theTTL buffer circuit 262. The output of circuit 262 on line 263 will beeither a logic high or "1" or a low or "0". These two conditionsindicate whether the off balance condition has been detected by the Yphotosensors, i.e., a high or "1" output condition indicates that thephotosensors are to the left relative to the center of tracking lines 76and 78 and, therefore, a move to the right is required for headcentering while a low or "0" output condition indicates that thephotosensors are to the right relative to the center of tracking lines76 and 78 and, therefore, a move to the left is required for headcentering. The inverted output at line 264 is shown but not used in thisembodiment.

Having explained the logic meaning of the output on line 263, referenceis again made to FIG. 6. There are two different types of alignmentconditions and two types of misalignment conditions to consider. Thefirst alignment type is where there is no dimensional offset, i.e., thecenter-to-center dimensions of the 1Y and 2Y, and 1Y' and 2Y' sensorpairs are identical disecting both tracking lines 76 and 78. This is thecase illustrated in FIG. 6. The second alignment type is where there isa dimensional mismatch, i.e., the center-to-center dimensions of the 1Yand 2Y, and 1Y' and 2Y' sensor pairs are not dissecting the trackinglines 76 and 78 but are shifted toward each other or away from eachother the same distance relative to the center axis of the trackinglines. Since sensors 1Y and 1Y' and sensors 2Y and 2Y' are summedtogether, the comparative outputs will be the same in this instance andno Y head position correction will be initiated.

The first misalignment condition is where sensor pairs 1Y and 2Y and 1Y'and 2Y' are respectively shifted in the same direction, either left orright, relative to the center axis of the tracking lines 76 and 78. Inthe condition where they are both shifted, for example, to the right asviewed in FIG. 6, the output level from the summed sensors 1Y and 1Y'will exceed that of summed sensors 2Y and 2Y' so that the output 263 ofcircuit 262 will indicate a high or "1" condition. This means that amove to the right for head positioning is required in order that thesensor pairs will be aligned again on the center axis of the trackinglines 76 and 78.

In the condition where they are both shifted to the left as viewed inFIG. 6, the output level from the summed sensors 2Y and 2Y' will exceedthat of the summed sensors 1Y and 1Y' so that the output 263 of thecircuit 262 will indicate a low or "0" condition. This means that a moveto the left for head positioning is required in order that the sensorpairs will be again aligned on the center axis of the tracking lines 76and 78.

The second misalignment condition is where one sensor pair is shiftedeither to the left or to the right of the center axis of one of thetracking lines while the other sensor pair is centered on the centeraxis of the other tracking line. For example, assume that the sensorpair 1Y' and 2Y' in FIG. 6 is centered on tracking line 78 as shown andassume further that the center of sensor pair 1Y and 2Y has shifted tothe left so that their center is centered over the left edge of trackingline 76. Since the outputs of sensors 1Y and 1Y' are summed together andthe outputs of sensors 2Y and 2Y' are summed together, the output levelfrom the summed sensors 1Y and 1Y' will exceed that of summed sensors 2Yand 2Y' so that the output 263 of circuit 262 will indicate a high or"1" condition. This means that a move to the right for head positioningis required in order that the sensor pairs will be aligned in the mannerexplained for the second type of alignment condition.

By the same token, assume that the sensor pair 1Y and 2Y in FIG. 6 iscentered on tracking line 76 as shown and assume further that the centerof sensor pair 1Y' and 2Y' has shifted to the right to be beyond theright edge of the tracking line 78 so that their center is off of thetracking line. The output level from the summed sensors 2Y and 2Y' willexceed that of summed sensors 1Y and 1Y' so that the output 263 ofcircuit 262 will indicate a low or "0" condition. This means that a moveto the left for head positioning is required in order that the sensorpairs will be aligned in the manner explained for the second type ofalignment condition.

In both of these examples for the second type of misalignment, theoffset of the misaligned sensor pair 1Y and 2Y or 1Y' and 2Y' (whicheverthe case) could be in the opposite Y direction relative to the centeraxis of the respective tracking line. In such cases, the corrective headpositioning move would be in the opposite direction relative to thedirections given in each of the above examples.

FIG. 10 discloses the initial signal processing circuitry for the X andX' photosensors. The circuit for sensor pairs 1X and 2X is the same forsensor pairs 1X' and 2X' so that only a single circuit need be shown.

The cathodes of photosensors 1X and 2X or 1X' and 2X' are connectedtogether to a positive voltage source. The anodes of these sensors areconnected to the inverting input of the conventional operationalamplifiers 268. The feedback RC filters 268' and these amplifiersprovide low bandwidth on the input signals from the photosensors X andX'. The output of these amplifiers on respective lines 272 and 273 issupplied via summing resistors 269 to a summing node 270 which isconnected to an input of summing amplifier 271. The other input ofamplifier 271 is connected to a reference voltage, e.g., --5.6 volts.The output of the summing amplifier 271 is connected via an isolationresistor and a positive voltage supply to the noninverting inputs ofoperational amplifiers 268. The purpose of this feedback, as mentionedin connection with FIG. 9, is to provide for automatic stabilizing ofthe sensed inputs independent of different light levels that thephotosensors might receive from the provided light sources. The feedbackamplifier 271 endeavors to maintain the summing node 270 at the samevoltage as the reference voltage, e.g., --5.6 volts, so that the outputof the amplifiers 268 are always at the same desired levels regardlessof changes in light source intensities over a period of time.

The adjusted outputs on lines 272 and 273 are supplied as inputs todifferential comparator 276 via RC filter 274. The output on line 277 ofcomparator 276 represents any difference in the light level sensed byphotosensor pairs 1X or 2X; 1X' or 2X' so that, for example, when 1Xsenses more light than 2X, the output on line 277 will be positive orwhen 2X senses more light than 1X, the output on line 277 will benegative. Comparator 276 has a small band of sensitivity so that verysmall differences between the signals to the inputs of comparator 276will provide a corresponding negative or positive output voltage on line277. Feedback resistor 276A for comparator 276 provides a hysteresisoperating effect for differential comparator 276. The change on line 277is supplied as an input to TTL buffer circuit 278. The noninvertedoutput 279 (or 279' in the case of X') of circuit 278 represents eithera logic high "1" or low or "0" condition. The inverting output 280 ofcircuit 278 is not used in this embodiment.

A high to low transition occurring on line 279 indicates a beginning ofa cycle 240 between adjacent registration marks 72 or 74, i.e., abalanced maximum light condition has been achieved by sensor pairs aspositioned in FIG. 6, while a low to high transition occurring on line279 indicates a transition occurring in the middle of a cycle 240wherein a balance minimize light condition has been achieved by sensorpairs as positioned over the center of a registration mark 72 or 74.

Reference is now made of FIG. 11 which is part of the circuit forposition controls 42-46 in FIG. 1. As will become evident, when thecircuit of FIG. 11 is employed as an embodiment for control 46, onlyoutput line 60, START TREATMENT, need be utilized. All the other outputsprovided on lines 291, 308, 315 and 316 together with the output on line60 are utilized for position controls 42 and 44.

The circuit of FIG. 11 relates to the START TREATMENT logic fordetermining (1) whether the initializing marks 71 have detected, (2)when the first registration mark 77 has been detected to determine thebeginning point on the web for the point of START TREATMENT, and (3) theenablement of appropriate functions at stations 12-16.

Start treatment logic 282 comprises four principle components, marksense logic 284, counting circuitry 286, sense mark test logic 288 andtreatment start point logic 290. Logic 284 consists of conventionaland/or gate and flip flop logic for receipt and interpretation of thethree inputs and sequencing the outputs to the counting circuitry 286.The counting circuitry 286 is adapted to count received pulses in amanner that provides a rough but accurate determination that a narrowinitializing mark 71 has been observed or that a wide registration mark72 has been observed. The sense mark test logic 288 is for determiningthat N "hits" have been made relative the detection of the series ofinitializing marks, i.e., that N initializing marks 71 have beendetermined to be in the view of the X sensor and that the circuit shouldbe initialized for the detection of a registration mark 74. The sensemark test logic 288 takes the hit count from circuit section 286, keepstrack of the number of hits made determines when N hits have been made.Treatment start point logic 290 permits the commencement of other logicfunctions after the first registration mark 77 has been observed.

The main purpose of mark sense logic 284 is to initially load and resetcounter 294, enable the counting of encoder pulses on line 40 uponreceipt of X sense mark signal 279 via filter 310 and line 311 and latchthe output in register 299 for the final value achieved in counter 294between X mark sense intervals.

Mark sense logic 284 has two inputs, WEB ADVANCE and X SENSE MARK. WEBADVANCE is an indication from the drive servo control 48 of theadvancement of the web 18.

When the signal, WEB ADVANCE, to mark sense logic 284 is low, logic 284is disenabled and, therefore, the start treatment logic 282 isdisenabled. When signal, WEB ADVANCE, goes high, mark sense logic 284 isplaced in a readiness state to be in a position to permit the functionof looking for tracking indicia 70.

When signal, WEB ADVANCE, goes high, a high (LOAD) is placed on logic284 output line 287 from mark sense logic 284 to permit counter 294 toload in the value for a narrow sense mark representative of aninitializing mark 71 from the memory switch 296 via gates 298.

Also, at this time the output TRACKING ON on line 291 of mark senselogic 284 goes high.

Line 295 is a handshaking and acknowledgement function between marksense logic 284 and test logic 288. When X sense mark signals from line279 are being received via line 311 in mark sense logic 284, mark senselogic 284 will provide an indication to sense mark test logic 288 tolook for the appropriate indication that a hit has been made and also toinitialize for counting N initialize marks.

Counting circuitry 286 comprises a counter that is able to determineroughly when a narrow mark interval or a wide mark interval has beenobserved. This function need not be highly accurate, i.e., it can bewithin 10 percent of the actual interval and confirm that theappropriate mark interval has been observed.

Memory switch 296 contains an 8 bit count representative of a narrowmark interval. This count value is present on gates 298, which functionlike a series of AND gates. The count value is placed into counter 294upon the LOAD received on line 287.

Output lines 279 and 279' from FIG. 10 are supplied as inputs to marksense sync filter 310. The function of filter is to synchronize thesesignals with the fast 3μ clock of the circuitry as well as determinethat the signals received are in fact sense mark intervals. This isaccomplished by determining that the mark sense intervals persist for atleast N number of clock pulses, e.g., 3 clock pulses. The X sense markoutput of sync filter 310 appears on line 311 which is an input to bothmark sense logic 284 and treatment start point logic 290. Upon receiptof this input, logic 284 places this input on output 292, COUNTER ENABLE(CTR EN) to AND gate 293. This output represents the cycle of one marksense interval so that as AND gate 293 is enabled by a negative goingmark interval transition, encoder clock pulses on line 40 will be fedinto counter 294 for counting. The count value in counter 294 isdecremented by the enabled encoder pulses for each mark sense intervaland value remaining per interval is latched into holding register 299via line 289. When the count value is decremented somewhere close to thevalue of a series of encoder pulses between mark sense intervals, eitherabove or below that value, the count held in register 299 will be at apoint close to either all binary 0's or 1's indicative that thedecremented count is on the verge of being a match with the count valuein memory switch 296. Since only a rough approximation is needed as tomark sense interval being detected, only the 5 most significant bits areexamined and held in register 300. When the 5 most significant bits areall binary 1's or 0's, a "hit" has been scored and the indication of a"hit" is supplied as an input on line 301 to sense mark test logic 288.

Note that if a "false" sense mark of different mark interval, e.g., ascratch or smudge on the web surface 17, were received at filter 310 andpast the verification test for N clock pulses, the counter 294 would beenabled via mark sense logic 284. However, counting circuitry 286 wouldwith high probability never score a hit since the mark sense intervalwould not roughly coincide with that for either a narrow or widetracking mark.

Further, to insure a narrow initializing mark has, in fact, been sensedby counting circuitry 288, several sense marks are verified to have beenobserved before sense mark test logic 288 makes a final determinationthat a series of initializing marks have, in fact, been observed. Thisdetermination is accomplished with the aid of two bit counter 303.

The binary count of two is loaded into counter 303 from memory switch305 at the start of this verification process. The loading of counter303 is accomplished by an enablement on line 304 (LOAD). The initialenablement or LOAD of counter 303 is accomplished with handshaking frommark sense logic 284 wherein upon the receipt of what appears to aninput from 311 of a mark sense interval, a signal on line 295initializes sense mark test logic 288 which includes the loading ofcounter 303.

When sense mark test logic 288 receives a "hit" on line 301, counter 303will be decremented via line 306 by a count of one. Three "hits" in arow on line 301 will cause an overfill in counter 303 with the spillover placed on output borrow line 307 of counter 303. Thus, three hitsmeans that three good representations of initializing marks 71 hasoccurred and that the beginning of a treatment is, indeed, intended andthat observation and verification of a wider registration mark 72 is inorder.

If three sense mark intervals do not occur in a row, sense mark testlogic 288 will enable 2 bit counter 303 via line 304 to reload itscontent with the count of two from memory switch 305. If further marksense intervals are not received on line 311 by mark sense logic 284,logic 284 will place a signal on line 295 to cause sense mark test logic288 to reinitialize for further narrow mark verification. Thisreinitialization includes the reloading of counter 303.

Once three hits in a row have been determined, the indication of whichappears on the borrow line 307 to logic 288, logic 288 will then providea signal on output line 302 to gates 298 to connect the wide count valuein memory switch 297 to appear on the gates 298. This value is an 8 bitcount representative of a wide mark interval, i.e., the mark interval ofa registration mark 72 or 74.

Memory selects 296 and 297, having selected values respectively fornarrow and wide mark sense intervals, can be preselected to any desirednumber value.

Additional narrow width sense intervals will be continually received atthis time, as there are usually more than three initializing marks 71 asillustrated in FIG. 5. Since counter 294 will is now be loaded with thewider sense mark value, a "hit" would not occur in counting circuitry286 due to the large value difference in count comparison therebymarking it impossible to reach an all binary 1's or 0s value in the fivemost significant bits in register 300.

When a wider registration mark is observed and the approximate value ofits mark interval is achieved when the five most significant bits inregister indicate either all binary 0's or 1's, an output on line 301will indicate that a "hit" has been made. Logic 288, having previouslyset output 302 high, will interpret the receipt of this "hit" as thefirst wide registration mark 77 from which a determination can be madeas to the precise point for START TREATMENT at 79 (see FIG. 5). At thistime, sense mark test logic 288 enables its output line 308 which isindicative of wide sense mark interval detection. This embodiment willenable treatment start point logic 290 to permit the initialization andfunctioning of other circuitry shown in FIGS. 13 and 14 to utilize thecontinually received sense mark data for determining stepper motor andcorrection adjustments to be made. The output on line 308 represents atracking acquisition signal (TRK ACQ) input to the circuitry in FIGS. 12and 13 which will be discussed later.

The enablement of logic 209 is responsible for several principlefunctions. This includes the initialization of the position servo drivesas well as the counting of a predetermined number of wide registrationmarks 72 to determine the START TREATMENT point 79. Logic 290 has acounter and memory switch similar to counter 303 and memory switch 305except that memory swtich in logic 290 is set to the number value "R",which is representative of the number of wide registration marks to theSTART TREATMENT point 79. When treatment start point logic 290 hasreceived via line 308 from sense mark test logic 288 a sufficient numberof detected mark sense intervals equal R registration mark senseintervals, logic 290 will enable the output line 60, START TREATMENT, tostation 16. Treatment start point logic 290 also loads the X and X'sense mark inputs on lines 311 and 312, respectively, onto lines 315 and316. These outputs, termed X MARK SIGNAL LOAD and X' MARK SIGNAL LOAD,are supplied as inputs to the circuitry shown in FIG. 14, which will bediscussed later.

Reference is now made to FIG. 12 which shows in more detail the sensorinterface and stepper control 106 of FIG. 3.

The sensor interface comprises control logic 320 that is conventionalcircuitry designed to interpret its inputs in a conventional manner toprovide velocity via line 330 and direction indication via line 331 toconventional stepper motor drive circuitry 322. Logic 320 has two manualinputs. There are the manual command left and right inputs 324 and 325which permit manual operation of stepper motor 205 whereby an operatoris permitted to manually initialize the lateral translation and positionof supply roll 20. Input 327 is the general logic clock input. Input 328is a disenabling input provided by a mechanical limit switch on system10 to prevent any operation of the supply roll stepper motor 205 whenthe supply roll 20 is not in postion or is being changed.

Input 308 is TRK ACQ from start treatment logic 282 of FIG. 11. This isan enablement input to control logic 320 to commence the sensingfunctions and relative to web position and lateral adjustment of supplyroll 20 as explained in connection with FIG. 3.

The inputs 221 and 222 from the limit sensor device 216 mounted on frame140 are also inputs to control logic 320.

As mentioned relative to FIG. 4, the optical edge sensor 225 produces asignal that is proportional to the amount of coverage of web 18 over thesensor detection surface as compared to the amount of coverage off ofthe web edge and exposed to light source 224. The proper edge positionfor web 18 can therefore be proportional to a predetermined voltagevalue on line 108 which can be set to the voltage value V_(REF). The setvalue for V_(REF) is compared with the voltage appearing on line 108 incomparator 332 which also includes comparator amplifier and Schmitttrigger. Comparator 332 functions in a similar manner as comparator 260and circuit 262 in FIG. 9 by providing hysteresis operating effect whichis representive of a "deadband" of operation for stepper motor 205 sothat the motor will not be placed in a "chatter mode", i.e., alternatelystep one direction and then the other in a continuous manner. The output326 of comparator 332, therefore, is a logic value of either are binary"0" or "1" indicative of the magnitude of the difference between sensorinput 167 and V_(REF) as well as whether the value for input 167 washigher or lower than the representative value for V_(REF). These valuesare interpreted by control logic 320 in a conventional manner into drivepulses for motor drive circuitry 322, the value of which is proportionalto the magnitude of offset from V_(REF). Also, the amount of sensorcoverage indicates which direction the motor drive circuitry 322 shoulddrive motor 205. Logic 320 is conventional configured logic used forsuch optical sensor applications to determine direction and magnitudeand comprises AND/OR gate logic and two flip flops to hold the state ofvarious input signals and interpret the signal sequence. The steppermotor drive circuitry 322 is conventional and comprises a high currentdriver having a four phase output to operate the unipolar four phasestepper motor 205. The four phase output is necessary for directioncontrol of motor 205.

As previously explained relative to description of FIG. 3, the limitsensor 216 provides for maximum limits of operation on motor 205 andprovides a starting or initialized position for lateral roll translationabove that achievable through line-of-site positions of the webtranslation via inputs 234 and 235. How this initialization is achievedfor the initialization of web guide servo control 102 is the same asdetailed in FIG. 13 relative to te operation of state sequencer 342 andinitialization control logic 346, although this Figure is directed toimplementations for the position controls 42 and 44.

FIG. 13 is logic block diagram representative of the position controllogic circuit 340 for use with either position control 42 or 44. Thefirst function to occur is that a command for initialization request isreceived by the logic circuit 340 to initialize the position of theprocessing station 12 or 14 or a station component by initial steppermotor translation, for example to a desired central or neutral position.The INIT REQUEST is received by the state sequencer 342 in circuit 340.Sequencer 342 is a control that has three output states, INIT MOVERIGHT, INIT MOVE LEFT and ENABLE TRACKING. These states are respectivelyoutputs 343, 344 and 345 of sequencer 342. These outputs are also inputsto initialization control logic 346. Output 344 is also an input to aninitialization left pulse counter 350 via AND gate 347 and input line348 to counter 350. Counter 350 is connected to memory switch 351 whichcontains a predetermined number value for input to counter 35. The countvalue represents the initialized position desired for the selectedposition of initialized translation.

Sequencer output line 345, ENABLE TRACKING, is also an enabling input totracking control logic 359.

State sequencer 342 and initialization control logic 346 are reset vialine 352. Reset places sequencer back into its first state position foractivation upon receipt of INIT REQUEST. Reset in logic 346 reloadscounter 350 via LOAD line 356.

Another input to the initialization control logic 346 include limitswitch status on line 354. Line 354 is also an input to state sequencer342 and tracking control logic 359. The inputs 157 and 158 to limitswitch sync 353 represent respectively maximum right and left limits oftravel for the stepper motors 62 and 64.

Three different clocks are involved in the operation of position controlcircuitry 340. There is the main system clock 333 KHz or clock 1, aslower clock, clock 2 (208 Hz) and much slower clock 3 (8 Hz). Clocks 1and 2 are inputs to initialization control logic 346. Clock 1 is also aninput to limit switch sync 353. Clock 2 is also an input to trackingclock speed select circuit 355. Slow clock 3 is also an input to circuit355.

The purpose of limit switch sync circuit 353 is to receive as an inputon either line 157 or line 148 an indication that a maximum limit hasbeen met at an appropriate limit switch sensor associated with eitherstepper motor 62 or 64, as the case may be. Circuit 353 merely syncs anincoming limit switch signal with the main system clock 1 to be insynchronization with the clocking of logic circuit 346. The indicationof limit switch status is set on line 354 to initialization logiccircuit 346 tracking control logic 359 and to state sequencer 342.

Initialization control logic circuit 346 has three outputs. The firstoutput is a command signal, LOAD, on line 356 to cause counter 350 toload the number value from memory switch 351. The second output is aninitializing INIT DIRECTION command on line 357 to an input of OR gate360. The third output is an initializing INIT PULSES command on line 358to an input of OR gate 362. The output on line 358 is also the otherinput of AND gate 347.

The outputs 363 and 364, TRK DIRECTION and TRK PULSE, of the trackingcontrol logic circuit 359 are the other inputs to OR gates 360 and 362,respectively.

Tracking clock speed select circuit 355 also has, as an input, line 308(TRK ACQ) from FIG. 11. As will be evident, this input provides anindication as to when either the clock 2 or clock 3 rate should beselected as an output on CLOCK SELECT line 365 to tracking control logiccircuit 359.

The other inputs to logic circuit 359 are line 291 (TRACKING ON) fromFIG. 11, or a control signal on line 263 from FIG. 9 or a control signalon line 400 from FIG. 14.

During initialization of the position of stepper drive motors 62 or 64,initialization control logic circuit 346 provides the INIT DIRECTION andINIT PULSES to the high current driver circuity 368 via lines 366 and367 respectively from the outputs of OR gates 360 and 362. The output ofcircuitry 368 is, therefore, the four phase lines that are representedas line 56 or 58 in FIG. 1, as the case may be, to the stepper servodrive motors 62 and 64.

After initialization is complete, the function of initialization controllogic circuit 346 terminates and the function of tracking control logic359 becomes operational based upon the sensing conditions of the Y andY' tracking of web tracking lines 76 and 78, for example, to providetracking direction, TRK DIRECTION, on lines 363 and 366 and trackingpulses, TRK PULSE, on lines 364 and 367 to drive circuitry 368.

An explanation will now be given relative to the overall operation ofthe position control logic circuit 340.

Reset via line 352 has been accomplished. Reset causes initializationlogic circuit to cause counter 350 to load in the number value containedin switch 351. Switch 351 may be selected to have any number that isrepresentative of a close approximation as where the sensor X & Y; X' &Y' will be fairly aligned to the tracking indicia 70. Reset at sequencer342 initializes its sequence so that the first operative output will beINIT MOVE RIGHT. Upon the receipt of an INIT REQUEST command at statesequencer 342, the sequencer enables output, INIT MOVE RIGHT on line343. This command is to move the station or station comonent controlledby stepper motor 62 or 64 from its present position clear to its maximumright position allowable by its respective limit switch. Upon INIT MOVERIGHT going high, logic circuit 346 provides a "right" INIT DIRECTIONcommand on lines 357 and 366 to motor drive circuitry 368. Also, logiccircuitry provides a continuous train of stepper pulses, INIT PULSES, onlines 358 and 367 to motor drive circuitry 368. Clock 2 clock rate isemployed to the stepper INIT PULSES on line 358 to swiftly carry outthis translation movement to the maximum right position.

Once the right position limit is reached, a limit switch signal via line157 is received at limit switch sync circuit 353 which provides anindication to initialization logic circuit 346 via line 354 that themaximum limit has been achieved and the output on line 358 of INITpulses at the clock 2 rate is terminated.

The receipt of this limit switch status at sequencer 342 provides a highon line 344, INIT MOVE LEFT. This output causes logic circuit 346 toissue INIT PULSES on line 358 at the clock 2 fast rate while providingan INIT DIRECTION indication on line 357 of move "left". The high onoutput 344 enables AND gate 347 and the pulses provided on line 358 arealso supplied to counter 350. Counter 350 is decremented until the countequals zero at which time a signal high or INIT COMPLETE, is provided onoutput line 349 from counter 350 to state sequencer 342. This signalcauses state sequencer 342 to place a high on output line 345 or ENABLETRACKING. The effect of this high is to disenable initalization controllogic circuit 346 and provide and enable to tracking control logiccircuit 359, indicating that initialization of translational positioningto a preselected position has been accomplished and signals developedfrom regular tracking functions via photosensors X and Y can now beperformed.

The last enablement input for tracking control logic circuit 359 isTRACKING ON on line 291 from the start treatment logic circuit 282 inFIG. 11. When this input is high, circuit 359 is enabled to receive Ytracking logic signals from the output of Y sensor interface circuit ofFIG. 9 on line 263. These signals, as previously indicated, are either alogic "0" or "1" and indicative of a one step movement respectivelyeither to the left or right dependent on the Y,Y' sensor relationship totracking lines 76 and 78 as explained in connection with FIGS. 6-8.

It will be recalled that when TRACKING ON is enabled, the searching forthe detection of narrow initializing marks 71 is enabled prior to thedetection of a first wide registration mark 77. During this period oftime, the output on line 308 or TRK ACQ is at a low. This causestracking clock speed select circuit to select the faster clock rate,clock 2, for CLOCK SELECT line 365 to place tracking control logiccircuit 359 in a high speed Y tracking mode. Thus, during STARTTREATMENT determination, THE RESPECTIVE position control 42 or 44 isactuated to swiftly permit step corrections to be applied by motor 62 or64. As Y tracking logic signals are received at input line 263 to logiccircuit 359, logic circuit 359 will issue a left or right directioncommand, TRK DIRECTION, on line 363 and a tracking pulse command, TRKPULSE, on line 364. The feeding of the tracking pulses will be at theclock 2 rate of the tracking pulses to the appropriate stepper motor 62or 64. The incremental steps provided by the adjustment of steppermotors 62 and 64 may be, for example, as small as one tenth of a mil.

Once the start treatment logic circuit 282 of FIG. 11 has achieved awide registration mark "hit" and enables output on line 308, TRK ACQ,will go high. This input high to tracking clock speed select circuit 352will place the slow clock rate of clock 3 on its output line 365 totracking control logic circuit 359 and place the tracking function intoa low speed tracking mode.

Reference is now made to FIG. 14 which discloses detail relating toanother embodiment for control 46 in FIG. 1. The X and X' MARK SIGNALLOAD respectively on lines 315 and 316 from start treatment logiccircuit 282 are inputs to the respective counters 370 and 372. Anotherinput to each of the counters received at 370 and 372 is from encoder 36via line 40 providing encoder pulses developed by the encoder workingoff the moving web 18. The encoder pulses decrement the respectivecounter 370 and 372. Counters 370 and 372 are loaded with a count valueequal to M encoder pulses from their respective memory switches 371 and373. As each X or X' MARK SIGNAL LOAD, representative of the end orbeginning of a mark sense interval, is inputted to the respectivecounters 370 and 372 with the preloaded M value, the encoder pulses online 40 decrement the counters until the next mark interval is receivedon their respective input lines 315 and 316. Any value remaining at thetime of the next mark sense interval is placed on respective outputlines 374 and 376.

As the X or X' sensor "see" the moving registation marks 72 and 74, aseries of mark sense transitions are created via the circuit shown inFIG. 10. This is because each of these sensors include a sensor pair anda balance of either light or dark produced from the sensor pair willcreate a signal transition so that the output signals, X and X' MARKSIGNAL LOAD will have a cycle 240 (FIG. 6) that begins and ends betweenthe spaced registration marks. The signal will have negative transitionsin the middle of white spacings between marks and positive transitionsin the middle of the dark marks. Thus, as the sensor pairs 1X and 2X,1X' and 2X' see a balance in maximum or minimum illumination, the signalswitches polarity. The series of pulses will, of course, depend upon thevelocity of the web 18. As an example, the typical mark sense cycle orinterval may be 0.16 inch and, therefore, 160 milliseconds period at aweb velocity 1 inch per sec or a 1.6 second period at a web velocity at0.1 inch per sec. The encoder on the other hand is capable of producing2,000 pulses per revolution.

The counters 370 and 372 count the encoder pulses between negativetransitions of mark sense intervals. It is a predetermined fact thatthere should be M encoder pulses per mark sense interval. Once theencoder pulses have been counted between mark sense intervals, the valueM is subtracted from the count. Any difference, i.e., any encoder pulsesremaining under the value of M or over the value of M represents error.This error represents the value for shrinkage or expansion of web 18.This error may be, for example, +1 or -1 or a larger value. This erroris representative of X dimensional changes from center to center of theregistration marks 72 or 74. By injecting correction pulses, such as, +1or -1, on line 60 to station 16, correctional functions can be made atstation 16 based upon dimensional changes in the X direction of the web,which changes can be accomplished on-the-fly.

It may be desirable that single increment corrections at a time of +1 or-1, which are equal to one encoder clock pulse, should be made on line60 visa-vis several correction pulses, as this provides some damping andprevents potential over correction.

Experience has shown that typical changes in web material shrinkage andexpansion comprising paper may be about 1 mil per foot of web length sothat the amount of correction needed is very small.

The unfortunate fact about the LEFT ERROR and RIGHT ERROR output on theoutput lines 374 and 376 from counters 370 and 372 is that the samplevalues, representative of web error, are not .[.be.]. free from signalnoise. As an actual example, assume the value for M happens to be 448pulses. Thus, where there is no dimensional change in the web, thereshould be 448 encoder pulses between negative mark sense intervals.Experience has shown that out of 448 pulses, a difference of ±8 encoderpulses may represent signal noise and the expected error may be only±0.02 of that value. This is a typical signal to noise value. The noisemay be caused by several factors including the treatment processesapplied to the web and the resolution or print clarity of the trackingindicia itself. Also, the X and X' sensors operate with some noise. Theremaining portion of the circuit diagram in FIG. 14 is devoted toeliminating this error from the mark sense interval error values orsamples on line 374 and 376.

As previously mentioned, the mark sense intervals are known to compriseM encoder pulses in the time frame intervals between the mark sensetransitions derived from the optical sensor pairs 1X and 2X; 1X' and2X'. If the web has stretched, there will be one or more encoder pulsesabove the value M between mark sense intervals. Conversely, if the webhas shrunk, there will be one or more encoder pulses below the value Mbetween mark sense intervals. These pulses above and below the value Mmay be termed samples. As indicated above, experience having shown thata major portion of the sample values is signal noise. The effect of thisnoise may be significantly removed by effectively averaging severalsamples together and making error corrections according to N samplescomprising a sample group. This is mathematically accomplished by takinga running average over N samples wherein a current sample is added tothe sample group and the oldest sample in the sample group is droppedout. One manner of mathamatically accomplishing this through logiccircuitry is by taking each current sample group and effectivelydividing by N, i.e., the number of samples in the group and then carryout a summation of these values in a summation circuit. The value in thesummation circuit will be the total value of error for the mark senseintervals over a series of N samples.

Another manner of mathamatically accomplishing this through logiccircuitry is illustrated in FIG. 14. As shown in FIG. 14, the samples onlines 374 and 376 are serially fed to delay 378 via gate 377 and line379. Line 379 is also directly connected to summation circuit 384. Gate377 is controlled by mode control 380 via line 383 which can permit thegate 377 to enable X ONLY samples, or X' ONLY samples or a combinationof both X and X' samples (CENTRAL) to delay 378. Mode control 380 alsoprovides the advantage of being able to select samples developed fromone side of web 18 when a failure exists in the detection circuits atthe other side of the web, e.g., light source failure depended upon bythe X sensors. The utility or utilizing both X and X' sources forsamples is taking into account more information relative to Xdimensional changes although, the use of one such sample source has beenfound sufficiently adequate.

Delay 378 comprises a shift register which can contain N samples at atime. In this manner, the samples are delayed in time compared to thesame samples on line 379. Before each cycle of operation, a currentsample is loaded into delay 378 from line 379 and the last one is loadedout on line 379. The values on line 379 are then converted to theircomplement value at complement 381 and provided on line 382 as thesecond output to summation circuit 384. The value in circuit 384represents the combined average running mean for the samples.

The bigger the sample group N, the more noise present in the samples maybe effectively averaged out. However, sample groups too large will takelonger to process the sample group and corrective action will beunreasonably delayed. The varying error over long web distance for whichcorrection is needed may be not applied in proximity to the affected websection. If both the amount and the "polarity" of the error is changing,tracking web dimensional error with large sample groups of errors is notpossible because the detected error and applied correction will come toolate at station 16.

Somewhere between a small and large sample group is a range of optimizedsample averaging. In the system disclosed in FIG. 14, N=16 was chosen.However, N=8 or 32 could also easily have been employed.

The combined average running mean in circuit 384 is then supplied online 388 to a summation circuit 386. In circuit 386, the running meanproduced in each cycle of operation of the delay 378 is added to arunning total value. This total value is called the sum of the runningmean.

The run output of circuit 386 is supplied on line 387 to comparator 388wherein the sum of the running mean is compared with an allowablereference error. The allowable reference error represents an allowableerror band, e.g., from -1→0→+1. If the summed value from summing circuit386 becomes equal to or greater than ±1, a correction command via line389 is given at circuit 390. The action taken is that a correction pulseis issued on line 60 to processing station 16. At the same time, thetotal sum value in the summation circuit 386 is decremented by the samecorrection amount, i.e., the sum of the running mean is decremented eachcycle by the value from correction circuit 390.

Line 383 from mode control 380 is also connected to comparator 388. Ifmode control 380 is set for X ONLY mode or X' ONLY mode, then thecomparison value representative of the allowable reference error will beto set to N. If mode control 380 is set for CENTRAL mode, then thecomparison value representative of the allowable reference error will beset to 2N since there are twice the samples involved in errorcorrection.

In FIG. 15 discloses another circuit implementation control 42 or 44 inFIG. 1 for supplying control signals on line 400 to the position controllogic circuit 340 in FIG. 13. This circuit implementation suppliescorrection signals for web skew in its path through system 10.

In FIG. 15, the X MARK SIGNAL LOAD on line 315 is supplied as a startsignal for counter 393. Counter 393 is loaded with a count value equalto M encoder pulses from memory switch 393A. As each X MARK SIGNAL LOADis inputted to counter 393, preloaded with the M value, the encoderpulses on line 40 decrement the counter. As soon as a signal, X' MARKSIGNAL LOAD, is received on line 316, the value in counter 393 islatched into register 394. This value then represents the phasedifference between an incoming X mark sense interval and an incoming X'mark sense interval and represents an output line 395 the difference indistantial amounts on one side of the web as compared to the other andis indicative that the web is slightly skewed in its path through system10.

These error values are fed into delay 396 which is the same as delay 378in FIG. 14. A running average over N samples is examined per cyclewherein a current error sample is added to the sample group via line 395into delay 396 and the oldest sample in the sample group is provided tothe complement circuit 397. The delay complement signal and the originalerror signal are added by adder 398. The value here represents thecombined average running mean. These values are added to a total valueby summation circuit 399 which provides the sum of the running mean.This total summed value is compared to an allowable reference error,e.g., from +1 to +1, in comparator 403 to produce a logic signal on line400 representative of a count value as measured in encoder pulses anddeterminative of whether X mark sense intervals are exceeding ordiminishing relative to X' sense mark intervals.

FIG. 18 details an implementation for the tension servo control 98 ofFIG. 1. The purpose of dancer roll 90 is .Iadd.to .Iaddend.remove anyloop that is .[.produce.]. .Iadd.produced .Iaddend.in the web during itsmovement through system 10. Better control is maintained on webmovement, particularly at higher velocities, keeping constant tension onthe web and, also, provide for lower inertia. If movement of the webmovement is primarily always at a slow velocity, the need for the dancerroll may be nonexistent.

Dancer roll 90 is pivotally supported for vertical movement on an arm401 between two support rolls 402 and 404. Arm 401 is biased onto thesurface of the web 18 by a preselected amount of force by compressionspring 406. This force is indicated by arrow 161. Arm 401 has its pivotpoint connected to a movable commutator 408 of a reostat 410. Reostat410 has linear resistance connected across a power source 412. As thetension and, thereof, the vertical elevation of dancer roll 90 variesvertically between rolls 402 and 404, commutator 408 will also moveproviding an analog output proportional to the movement of arm 401. Thisoutput on line 96 is supplied to a comparator 414 which may comprise theinverting input of a differential amplifier. The signal on line 412 iscompared with a positive reference value, V_(R) which is supplied to thenoninverting input of comparator 414 via switch 416. The value V_(R),represents the value of the preselected tension desired on the surfaceof web 18 by dancer roll 90. The compared output provided on line 418is, therefore, representative of differences, either negative orpositive, from the predetermined value. This output is supplied as aninput to the motor driver circuit 420 for supply roll motor 19. Circuit420 provides conventional motor drive circuitry for drive motor 19 butalso includes a power amplifier which takes the signal on line 418 andincreases or decreases the constant torque via line 100 on motor 19represented by arrow 20' according to whether the compared deviationfrom the desired dancer roll tension is respectively too little or toomuch.

While the invention has been described in conjunction with specificembodiments, it is evident that many alternatives, modifications andvariations will be apparent to those skilled in the art in light of theforegoing description. Accordingly, it is intended to embrace all suchalternatives, modifications, and variations as fall within the spiritand scope of the appended claims.

What is claimed is:
 1. Web tracking system for a continuous web ofmaterial which is transported from a supply roll means to a takeup rollmeans along a predetermined path via one or more sequentially positionedprocessing stations to treat said web comprisingaligned tracking indiciacomprising a line of registration marks of substantially uniform spacingand width along each edge of said web, means mounted relative to thepassage of said web to optically observe said tracking indicia alongeach of said web edges as said web is transported along said path andproduce informational tracking signals based upon the passage of saidtracking indicia relative to said observation means, circuit meansresponsive to said informational signals to produce control signalsindicative of changes in the lateral and longitudinal dimensions of saidweb, means to provide relative translation between said processingstations and said web along said path, said translation means responsiveto said control signals to translate said processing stations accordingto changes in the lateral and longitudinal dimensions of said web. 2.The system of claim 1 wherein said translation means comprises web guideservo control to laterally translate a web supply roll at said supplymeans relative to said processing station.
 3. The system of claim 1wherein said translation means includes a processing station lateralposition control to laterally postion said processing station relativeto said web in said path.
 4. The system of claim 1 wherein saidtranslation means includes a processing station rotational positioncontrol to rotate said processing station relative to said web in saidpath.
 5. The system of claim 1 wherein said tracking marks compriseregistration marks of equal spacing and width.
 6. The system of claim 5wherein said registration marks are .[.preceeded.]. .Iadd.preceded.Iaddend.by a plurality .Iadd.of .Iaddend.aligned initializing marks atthe beginning of said web, said initializing marks having a differentgeometric shape compared to said registration marks.
 7. The system ofclaim 6 wherein said different geometric shape comprises a differentmark width.
 8. The system of claim 6 wherein the change from saidinitializing marks to said registration marks is indicative of astarting point for determining a particular location further along saidweb.
 9. The system of claim 1 wherein determination of dimensionalchanges by said circuit means via said observation means is accomplishedby monitoring the spacing between registration marks along at least oneedge of said web indicative of changes in web length and monitoringlateral shift of said lines of registration marks relative to itsrespective observation means at both edges of said web indicative ofeither a change in web width or a lateral shift of said web relative tosaid observation means.
 10. The system of claim 1 wherein said alignedtracking indicia comprisesa line of registration marks of substantiallyuniform spacing and width along each edge of said web for purposes ofmonitoring dimensional changes in the length of said web and a solidline along each edge of said web ajacent to said line of registrationmarks for purposes of monitoring dimensional changes in the width ofsaid web.
 11. The system of claim 10 wherein determination ofdimensional changes by said circuit means via said observation means isaccomplished by monitoring the spacing between registration marks alongat least one edge of said web indicative of changes in web length andmonitoring lateral shift of said solid lines relative to its respectiveobservation means at both edges of said web indicative of either achange in web width or a lateral shift of said web relative to saidobservation means.
 12. Web tracking system for a continuous web ofmaterial which is transported from a supply roll means to a takeup rollmeans along a predetermined path via one or more sequentially positionedprocessing stations to treat said web comprisingaligned tracking indiciaalong at least one edge of said web, said tracking indicia comprising aplurality of aligned of registration marks of substantially uniformspacing and width and a plurality of aligned initializing markspreceding said registration marks and having a different geometric shapecompared to said registration marks, means mounted relative to thepassage of said web to optically observe said tracking indicia as saidweb is transported along said path and produce .[.an.]. informational.[.signal .]. .Iadd.signals .Iaddend.indicative of .[.distant.]..Iadd.predetermined .Iaddend.lengths along said .[.medium.]. .Iadd.web.Iaddend.useful at one or more of said processing stations, circuitmeans responsive to said informational .[.signal.]. .Iadd.signals.Iaddend.indicative of the recognition of said initalizing marks anddeterminative of the point of transition from the last of saidinitializing marks to the first of said registration marks, said circuitmeans further determinative of the distance between said transitionpoint and a predetermined point further along said registration markswherein the treatment of said web is desired to be initiated relative toany one of said stations.
 13. In the web tracking system of claim 12wherein said initializing marks are identical to said registration marksbut are of a different dimensional width.
 14. In the web tracking systemof claim 13 wherein said initializing marks are smaller dimensionalwidth than said registration marks. .Iadd.15. The system of claim 1wherein said circuit means comprises means for comparing saidinformational signals with a known value to produce said control signalsrepresenting a dimensional change in the lateral and longitudinaldirection of the web,means for averaging a plurality of said controlsignals together to produce a composite error signal representative of arunning average in the lateral and longitudinal shrinkage or expansionof said web, and means for utilizing said composite error signal toadjust the relative positional relationship of said web relative to oneor more of said processing stations to compensate for any changes thathave occurred in web lateral and longitudinal dimension. .Iaddend..Iadd.16. The system of claim 1 wherein said circuit means comprisesmeans to correct for misalignment between the lateral positionalrelationship of said web relative to at least one of said processingstations. .Iaddend. .Iadd.17. The system of claim 12 wherein saidcircuit means comprises means for comparing said informational signalswith a known value to produce control signals representing a dimensionalchange in the lateral and longitudinal direction of the web,means foraveraging a plurality of said control signals together to produce acomposite error signal representative of a running average in thelongitudinal shrinkage or expansion of said web, and means for utilizingsaid composite error signal to adjust the relative positionalrelationship of said web relative to one or more of said processingstations to compensate for any changes that have occurred in weblongitudinal dimension. .Iaddend. .Iadd.18. The system of claim 17wherein said utilizing means comprises means to correct for lateralmisalignment between the lateral positional relationship of said webrelative to at least one of said processing stations. .Iaddend..Iadd.19. The system of claim 12 wherein there are aligned along atleast two edges of said web, means to correct for lateral misalignmentbetween (a) the lateral positional relationship of said web relative toone or more of said processing stations and (b) the lateral dimensionalrelationship of said web due to changes in the lateral shrinkage orexpansion of said web relative to at least one of said processingstations. .Iaddend. .Iadd.20. The system of claim 12 wherein there ismeans to translation between at least one of said processing stationsand said web along said path. .Iaddend. .Iadd.21. The system of claim 20wherein said translation means comprises web guide servo control tolaterally translate said supply roll means relative to one or more ofsaid processing stations. .Iaddend. .Iadd.22. The system of claim 20wherein said translation means comprises a processing station lateralposition control means to laterally position said processing stationrelative to said web in said path. .Iaddend. .Iadd.23. The system ofclaim 20 wherein said translation means comprises a processing stationrotational position control to rotate said processing station relativeto said web in said path. .Iaddend. .Iadd.24. The system of claim 12wherein said tracking indicia comprise registration marks ofsubstantially equal spacing and width. .Iaddend. .Iadd.25. The system ofclaim 12 wherein said different geometric shape comprises a differentdimensional width. .Iaddend. .Iadd.26. A system for controlling thetrack or position of a continuous web of material traveling from asupply roll to a takeup roll along a predetermined path via one or moresequentially positioned processing stations for selectively treating aportion of the web comprisingaligned tracking indicia along at least oneregion of said web portion, means mounted relative to the passage ofsaid web to observe said tracking indicia as said web is transportedalong said path and produce informational tracking signals based uponthe passage of said tracking indicia relative to said observationsmeans, circuit means for comparing said signals with a known value toproduce error signals representing a dimensional change in thelongitudinal direction of the web, means for averaging a plurality ofsaid error signals together to produce a composite error signalrepresentative of a running average in longitudinal shrinkage orexpansion of said web portion, and means for utilizing said compositeerror signal to adjust the relative positional relationship of said webportion relative to one or more of said processing stations tocompensate for any changes that have occurred in web longitudinaldimension. .Iaddend. .Iadd.27. The system of claim 26 wherein saidutilizing means includes means to correct for lateral misalignmentbetween the lateral positional relationship of said web portion relativeto one or more of said processing stations. .Iaddend. .Iadd.28. Thesystem of claim 26 wherein there are aligned tracking indicia along atleast two regions of said web portion, said utilizing means includingmeans to correct for lateral misalignment between (a) the lateralpositional relationship of said web portion relative to one or more ofsaid processing stations or (b) the lateral dimensional relationship ofsaid web portion due to changes in the lateral shrinkage or expansion ofsaid web portion relative to one or more of said processing stations..Iaddend. .Iadd.29. The system of claim 26 wherein said utilizing meansincludes means to provide relative translation between at least one ofsaid processing stations and said web portion along said path. .Iaddend..Iadd.30. The system of claim 29 wherein said translation meanscomprises web guide servo control to laterally translate said supplyroll relative to said processing station. .Iaddend. .Iadd.31. The systemof claim 29 wherein said translation means comprises a processingstation lateral position control means to laterally position saidprocessing station relative to said web portion in said path. .Iaddend..Iadd.32. The system of claim 29 wherein said translation meanscomprises a processing station rotational position control to rotatesaid processing station relative to said web portion in said path..Iaddend. .Iadd.33. The system of claim 26 wherein said tracking indiciacomprise registration marks of substantially equal spacing and width..Iaddend. .Iadd.34. The system of claim 26 wherein said tracking indiciaare preceded by initializing means indicative of a start point forprocessing of said web relative to any one of said processing stationsand in conjunction with said utilizing means determinative of thedistance between said start point and a predetermined point furtheralong said tracking indicia wherein the treatment of said web is desiredto be initiated relative to any one of said processing stations..Iaddend. .Iadd.35. The system of claim 34 wherein said initializingmeans comprises at least one tracking indicia. .Iaddend. .Iadd.36. Thesystem of claim 26 which includesincrement means to translatelongitudinally, laterally or rotationally one or more of said processingstations or a component part of one or more of said processing stations,said observation means including paired sensing means positionedrelative to said tracking indicia, the outputs of corresponding pairs ofsaid paired sensing means coupled to produce separate summed outputscomprising said information signals, differences in magitude betweensaid information signals indicative of the changes in said positionalrelationship. .Iaddend.
 37. Web tracking system for a continuous web ofmaterial which is transported from a supply roll means to a takeup rollmeans along a predetermined path via one or more sequentially positionedprocessing stations to treat regional portions of said web and wherein adesired positional relationship is to be maintained between said web andone or more of said processing stations and comprisingaligned trackingindicia continuous or closely spaced, intermittently continuouslongitudinally along at least two regions of said web adjacent to saidtreated regional portions, means mounted relative to the passage of saidweb to continuously observe said tracking indicia as said web istrasnported along said path and simultaneously produce on-the-flyinformational signals based upon the passage of said tracking indiciarelative to said observations means as said treated regional portionsmove into and through one or more of said processing stations, means forutilizing said signals to correct on-the-fly for misalignment in thepositional relationship of said web relative to at least one of saidprocessing stations due to shrinkage or expansion changes in said web ineither the lateral or longitudinal dimensions of said web or in bothdimensions thereof. .Iadd.38. The system of claim 37 wherein saidcircuit means comprises means for comparing said informational signalswith a known value to produce said control signals representing adimensional change in the longitudinal direction of the web,means foraveraging a plurality of said control signals together to produce acomposite error signal representative of a running average in thelongitudinal shrinkage or expansion of said web, and means for utilizingsaid composite error signal to adjust the positional relationship ofsaid web relative to one or more of said processing stations tocompensate for said changes that have occurred in web longitudinaldimension. .Iaddend. .Iadd.39. The system of claim 37 wherein saidutilizing means includes means to provide relative translation betweenat least one of said processing stations and said web along said path..Iaddend. .Iadd.40. The system of claim 39 wherein said translationmeans comprises web guide servo control to laterally translate saidsupply roll means relative to one or more of said processing stations..Iaddend. .Iadd.41. The system of claim 39 wherein said translationmeans comprises a processing station lateral position control means tolaterally position said processing station relative to said web in saidpath. .Iaddend. .Iadd.42. The system of claim 39 wherein saidtranslation means comprises a processing station rotational positioncontrol to rotate said processing station relative to said web in saidpath. .Iaddend. .Iadd.43. The system of claim 37 wherein said trackingindicia are preceded by initializing means indicative of a start pointfor processing of said web relative to any one of said processingstations and in conjunction with said utilizing means determinative ofthe distance between said start point and a predetermined point furtheralong said tracking indicia wherein the treatment of said web is desiredto be initiated relative to any one of said processing stations..Iaddend. .Iadd.44. The system of claim 43 wherein said initializingmeans comprises at least one tracking indicia. .Iaddend. .Iadd.45. Thesystem of claim 37 which includesincrement means to translatelongitudinally, laterally or rotationally one or more of said processingstations or a component part of one or more of said processing stations,said observation means including paired sensing means positionedrelative to each of said tracking indicia, the outputs of correspondingpairs of said paired sensing means coupled to produce separate summedoutputs comprising said information signals, differences in magnitudebetween said information signals indicative of the changes in saidpositional relationship. .Iaddend. .Iadd.46. Web tracking system for acontinuous web of material transported from a supply roll means to atakeup roll means along a predetermined path via one or moresequentially positioned processing stations to treat said web wherein adesired positional relationship is to be maintained between said web andone or more of said stations and comprisingaligned tracking indiciaalong at least two regions of said web, means mounted relative to thepassage of said web to observe said tracking indicia as said web istransported along said path and produce informational signals based uponthe passage of said tracking indicia and a web edge relative to saidobservations means, means for utilizing said signals to correct formisalignment in the positional relationship of said web relative to atleast one of said processing stations due to changes in the lateralpositional relationship of said web relative to said processing stationor due to shrinkage or expansion changes in said web in either thelateral and longitudinal dimensions of said web or in both dimensionsthereof. .Iaddend. .Iadd.47. The system of claim 46 wherein said circuitmeans comprises means for comparing said informational signals with aknown value to produce said control signals representing a dimensionalchange in the longitudinal direction of the web, p1 means for averaginga plurality of said control signals produce a composite error signalrepresentative of a running average in the longitudinal shrinkage orexpansion of said web, and means for utilizing said composite errorsignal to adjust the positional relationship of said web relative to oneor more of said processing stations to compensate for said changes thathave occurred in web longitudinal dimension. .Iaddend. .Iadd.48. Thesystem of claim 46 wherein said utilizing means includes means toprovide relative translation between at least one of said processingstations and said web along said path. .Iaddend. .Iadd.49. The system ofclaim 48 wherein said translation means comprises web guide servocontrol to laterally translate said supply roll means relative to one ormore of said processing stations. .Iaddend. .Iadd.50. The system ofclaim 48 wherein said translation means comprises a processing stationlateral position control means to laterally position said processingstation relative to said web in said path. .Iaddend. .Iadd.51. Thesystem of claim 48 wherein said translation means comprises a processingstation rotational position control to rotate said processing stationrelative to said web in said path. .Iaddend. .Iadd.52. The system ofclaim 46 wherein said tracking indicia are preceded by initializingmeans indicative of a start point for processing of said web relative toany one of said processing stations and in conjunction with saidutilizing means determinative of the distance between said start pointand a predetermined point further along said tracking indicia whereinthe treatment of said web is desired to be initiated relative to any oneof said processing stations. .Iaddend. .Iadd.53. The system of claim 52wherein said initializing means comprises at least one tracking indicia..Iaddend. .Iadd.54. The system of claim 46 which includesincrement meansto translate longitudinally, laterally or rotationally one or more ofsaid processing stations or a component part of one or more of saidprocessing stations, said observation means including paired sensingmeans positioned relative to each of said tracking indicia, the outputsof corresponding pairs of said paired sensing means coupled to produceseparate summed outputs comprising said information signals, differencesin magnitude between said information signals indicative of the changesin said positional relationship. .Iaddend. .Iadd.55. The system of claim46 wherein said aligned tracking indicia are continuous or closelyspaced, intermittently continuous indicia longitudinally along said atleast two regions adjacent to regional portions of said web to betreated at said processing stations, said mounted means to continuouslyobserve said longitudinally continuous tracking indicia andsimultaneously produce on-the-fly said information signals as saidtreated regional portions move into and thorugh one or more of saidprocessing stations. .Iadd.56. Web tracking system for a continuous webof material which is transported from a supply roll means to a takeuproll means along a predetermined path via one or more sequentiallypositioned processing stations to treat regional portions of said weband wherein a desired positional relationship is to be maintainedbetween said web and one or more of said processing stations andcomprisingaligned tracking indicia continuous or closely spaced,intermittently continuous longitudinally along at least one region ofsaid web adjacent to said treated regional portions, means mountedrelative to the passage of said web to continuously observe saidtracking indicia as said web is transported along said path andsimultaneously produce on-the-fly informational signals based upon thepassage of said tracking indicia and a web edge relative to saidobservations means as said treated regional portions move into andthrough one or more of said processing stations, means for utilizingsaid signals to correct on-the-fly for misalignment in the positionalrelationship of said web relative to at least one of said processingstations due to changes in the lateral positional relationship of saidweb relative to said processing station and due to shrinkage orexpansion changes in said web in the longitudinal dimension of said web..Iaddend. .Iadd.57. The system of claim 56 wherein said circuit meanscomprises means for comparing said informational signals with a knownvalue to produce said control signals representing a dimensional changein the longitudinal direction of the web,means for averaging a pluralityof said control signals together to produce a composite error signalrepresentative of a running average in the longitudinal shrinkage orexpansion of said web, and means for utilizing said composite errorsignal to adjust the positional relationship of said web relative to oneor more of said processing stations to compensate for said changes thathave occurred in web longitudinal dimension. .Iaddend. .Iadd.58. Thesystem of claim 56 wherein said utilizing means includes means toprovide relative translation between at least one of said processingstations and said web along said path. .Iaddend. .Iadd.59. The system ofclaim 58 wherein said translation means comprises web guide servocontrol to laterally translate said supply roll means relative to one ormore of said processing stations. .Iaddend.
 0. The system of claim 58wherein said translation means comprises a processing station lateralposition control means to laterally position said processing stationrelative to said web in said path. .Iadd.61. The system of claim 58wherein said translation means comprises a processing station rotationalposition control to rotate said processing station relative to said webin said path. .Iaddend. .Iadd.62. The system of claim 56 wherein saidtracking indicia are preceded by initializing means indicative of astart point for processing of said web relative to any one of saidprocessing stations and in conjunction with said utilizing meansdeterminative of the distance between said start point and apredetermined point further along said tracking indicia wherein thetreatment of said web is desired to be initiated relative to any one ofsaid processing stations. .Iaddend. .Iadd.63. The system of claim 62wherein said initializing means comprises at least one tracking indicia..Iaddend. .Iadd.64. The system of claim 56 which includesincrement meansto translate longitudinally, laterally or rotationally one or more ofsaid processing stations or a component part of one or more of saidprocessing stations, said observation means including paired sensingmeans positioned relative to said tracking indicia, the outputs ofcorresponding pairs of said paired sensing means coupled to produceseparate summed outputs comprising said information signals, differencesin magnitude between said information signals indicative of the changesin said positional relationship. .Iaddend. .Iadd.65. Web tracking systemfor a continuous web of material which is transported from a supply rollmeans to a takeup roll means along a predetermined path via one or moresequentially positioned processing stations to treat said web wherein adesired positional relationship is to be maintained between said web andone or more of said stations and comprising aligned tracking indiciaalong at least two regions of said web, means mounted relative to thepassage of said web to observe said tracking indicia as said web istransported along said path and produce informational signals based uponthe passage of said tracking indicia and a web edge relative to saidobservations means, means for utilizing said signals to correct formisalignment in the positional relationship of said web relative to atleast one of said processing stations due to changes in the lateralpositional relationship of said web relative to said processing stationor due to shrinkage or expansion changes in said web in the lateraldimension of said web or due to both of said changes. .Iaddend..Iadd.66. The system of claim 65 wherein said circuit means comprisesmeans for comparing said informational signals with a known value toproduce said control signals representing a dimensional change in thelongitudinal direction of the web, means for averaging a plurality ofsaid control signals together to produce a composite error signalrepresentative of a running average in the longitudinal shrinkage orexpansion of said web, and means for utilizing said composite errorsignal to adjust the positional relationship of said web relative to oneor more of said processing stations to compensate for said changes thathave occurred in web longitudinal dimension. .Iaddend. .Iadd.67. Thesystem of claim 65 wherein said utilizing means includes means toprovide relative translation between at least one of said processingstations and said web along said path. .Iaddend. .Iadd.68. The system ofclaim 67 wherein said translation means comprises web guide servocontrol to laterally translate said supply roll means relative to one ormore of said processing stations. .Iaddend. .Iadd.69. The system ofclaim 67 wherein said translation means comprises a processing stationlateral position control means to laterally position said processingstation relative to said web in said path. .Iaddend. .Iadd.70. Thesystem of claim 67 wherein said translation means comprises a processingstation rotational position control to rotate said processing stationrelative to said web in said path. .Iaddend. .Iadd.71. The system ofclaim 65 wherein said tracking indicia are preceded by initializingmeans indicative of a start point for processing of said web relative toany one of said processing stations and in conjunction with saidutilizing means determinative of the distance between said start pointand a predetermined point further along said tracking indicia whereinthe treatment of said web is desired to be initiated relative to any oneof said processing stations. .Iaddend. .Iadd.72. The system of claim 71wherein said initializing at least one tracking indicia. .Iaddend..Iadd. . The system of claim 65 which includesincrement means totranslate longitudinally, laterally or rotationally one or more of saidprocessing stations or a component part of of one or more of saidprocessing stations, said observation means including paired sensingmeans positioned relative to each of said tracking indicia, the outputsof corresponding pairs of said paired sensing means coupled to produceseparate summed outputs comprising said information signals, differencesin magnitude between said information signals indicative of the changesin said positional relationship. .Iaddend. .Iadd.74. The system of claim65 wherein said aligned tracking indicia are continuous or closelyspaced, intermittently continuous indicia longitudinally along said atleast two regions adjacent to regional portions of said web to betreated at said processing stations, said mounted means to continuouslyobserve said longitudinally continuous tracking indicia andsimultaneously produce on-the-fly said informational signals as saidtreated regional portions move into and through one or more of saidprocessing stations. .Iaddend. .Iadd.75. Web tracking system for acontinuous web of material transported from a supply roll means to atakeup roll means along a predetermined path via one or moresequentially positioned processing stations to treat said webcomprisingaligned tracking indicia along at least one region of saidweb, initializing means preceding said aligned tracking indicia, meansmounted relative to the passage of said web to optically observe saidtracking indicia as said web is transported along said path and produceinformational signals indicative of the longitudinal dimension alongsaid web useful at one or more of said processing stations, circuitmeans responsive to said informational signals indicative of therecognition of said initializing means and determinative of the point oftransition from said initializing means to said tracking indicia, saidcircuit means further determinative of the distance between saidtransition point and a predetermined point further along said trackingindicia wherein the treatment of said web is desired to be initiatedrelative to any one of said stations. .Iaddend. .Iadd.76. The system ofclaim 75 wherein said initializing at least one registration mark onsaid web. .Iaddend. .Iadd.77. The system of claim 75 whichincludespaired sensing means positioned relative to said trackingindicia, the outputs of corresponding pairs of said paired sensing meanscoupled to produce separate summed outputs comprising said informationsignals, differences in magnitude between said information signalsindicative of said point of transition. .Iaddend.